Replaces the static Duplicate() method.

To make things simpler, AllocatedString is now a non-template class.

release v0.22.4

The Google overlords require me to change to 29 or else I can't upload
new releases to Google Play.

 https://developer.android.com/distribute/best-practices/develop/target-sdk

Increasing the protocol version to 0.22.4 to allow clients to detect
this feature.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1038

Of course, it should do that!

I havn't yet figured out how to use Android's system CA certificates
with CURL/OpenSSL, so a temporary workaround is to disable verify_peer
by default.  The data MPD transfers isn't extremely important, so the
servers's authenticity isn't extremely important either.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1059

Regression by commit cd4b673b

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1060

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1048

This properly prints the "Time"/"duration" values for songs in virtual
CUE folders.

This is loosely related to
https://github.com/MusicPlayerDaemon/MPD/issues/1048

`PRIoffset` was wrong, because it expects an `offset_type`
(i.e. `uint64_t`).  This broke on 32 bit machines where `size_t` has
32 bits.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1058

"The documentation for mpd.conf still links to https://replaygain.org
– according to archive.org, this domain has been defunct since
2014-09-14, shortly after got domain squatted and ever since hosts
dubious content."

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1050

The `{TAG} {NEEDLE}` input format documented seems to be a holdover
of pre-0.21 filters, and the commands support the new format.

Found with cppcoreguidelines-interfaces-global-init
Signed-off-by: Rosen Penev <rosenp@gmail.com>

If an InjectEvent callback schedules a timer, the loop will restart,
but the "busy" flag is still false.  The fix is to move the "again"
check before the "busy" setting.